Implant with ability to capture extravasating fixation medium

ABSTRACT

A surgical implant with recesses adapted to capture fixation medium that extravazates during implantation. The implant includes an elongated stem having a distal tip configured for insertion into an implant receiving area of a patient. A collar designed to house recesses for capturing extravazating fixation medium is attached on the stem. The collar can be fixed to the stem by a separable collar-engagement feature or the collar can be fixed to the stem via structures on the stem.

FIELD OF INVENTION

The invention relates to surgical implants and their ability to capturefixation media extravasating from an implant fixation location.

BACKGROUND OF THE INVENTION

Surgical implants are used to replace various joints and otheranatomical features. During implantation of certain implants, it iscommon to use a fixation medium in order to improve adhesion andfixation of the surgical implant within an implant receiving area orcavity of a patient. For a class of implants having hybrid stems, aportion of the stem is designed to be fixed to bone with a fixationmedium while another portion of the implant is designed to allow forbony ingrowth or ongrowth. During implantation of hybrid stems, excessfixation medium may be displaced from inside the cavity, whichdisplacement is also referred to as extravasation, and flow overportions of the surgical implant that are configured to promote boneingrowth therein. When in contact with bone ingrowth surfaces, suchfixation medium may inhibit the growth of bone onto and into the implantbecause it covers the surface of the implant configured to receive boneingrowth. This, in turn, reduces the volume of bone ingrowth area thatis available for bone to grow into. As a result, the fixation of theimplant is reduced and likelihood of failure of the implant isincreased. Thus, there is a need in the art for a surgical implant thatis capable of capturing excess fixation medium so as to help prevent thebone ingrowth area from being coated by fixation medium.

SUMMARY OF THE INVENTION

In an embodiment, the present invention includes a method of using animplant to collect excess fixation medium extravasating from an implantreceiving area during introduction of the implant, the method comprisingintroducing the implant into the implant receiving area, wherein theimplant includes a collar having at least one recess capable ofreceiving extravasating fixation medium, and wherein the at least onerecess is located on a surface of the collar facing the implantreceiving area, and the at least one recess receiving excess fixationmedium.

In further embodiments, the method includes the step of introducingfixation medium to the implant receiving area prior to the introducingstep. In other embodiments, the implant includes an elongated stemhaving a distal tip and a proximate end opposite the distal tip. In yetfurther embodiments, the stem includes one or more flanges and thecollar includes an inner region with one or more interior threadslocated on at least a portion of the inner region, and wherein theinterior threads are sized and shaped to accommodate the one or moreflanges. In yet further embodiments, the assembling step furtherincludes introducing the collar over the stem and translating the collaralong the stem until the collar reaches the one or more the flanges ofthe stem and then rotating either the collar or the stem or both toengage the one or more interior threads and the one or more flanges. Inyet further embodiments, the assembling step further includes rotatingthe collar approximately three-quarters of a full rotations. In yetfurther embodiments, a collar-engagement feature is provided and thestem includes a radially projecting shoulder. In yet furtherembodiments, the collar and the collar-engagement feature are assembledover the shoulder prior to insertion into the implant receiving area ofa patient.

In other embodiments, the present invention includes a method of usingan implant to collect excess fixation medium extravasating from animplant receiving area during introduction of the implant, the methodcomprising assembling the implant, introducing the implant into theimplant receiving area, wherein the implant includes a collar having atleast one recess capable of receiving extravasating fixation medium, andwherein the at least one recess is located on a surface of the collarfacing the implant receiving area, and the at least one recess receivingexcess fixation medium.

In further embodiments, the method further comprises the step ofintroducing an amount of fixation medium to the implant receiving areaprior to the introducing step. In yet further embodiments, the implantfurther includes an elongated stem having a distal tip and a proximateend opposite the distal tip. In yet further embodiments, the assemblingstep includes attaching the collar to the stem. In yet furtherembodiments, the introducing assembling step further includes acollar-engagement feature having internal threads and the collar furtherincludes external threads, and wherein the external threads of thecollar are rotatably engaged with the internal threads of thecollar-engagement feature. In yet further embodiments, the implantincludes a radially projecting shoulder over which the collar-engagementfeature and the collar can be fixed. In yet further embodiments, thestem includes one or more flanges and the collar includes an innerregion with one or more interior threads located on at least a portionof the inner region, and wherein the interior threads are sized andshaped to accommodate the one or more flanges. In yet furtherembodiments, the assembling step further includes introducing the collarover the stem and translating the collar along the stem until the collarreaches the one or more the flanges of the stem and then rotating eitherthe collar or the stem or both to engage the one or more interiorthreads and the one or more flanges. In yet further embodiments, theassembling step further includes a rotation of either the collar or thestem approximately three-quarters of a full rotation.

In other embodiments, the present invention includes a method of usingan implant to collect excess fixation medium extravasating from animplant receiving area during introduction of the implant, the methodcomprising assembling the implant, introducing the implant into theimplant receiving area, wherein the implant includes a collar havingmeans for receiving extravasating fixation medium, and wherein the meansfor receiving extravasating fixation medium is located on a surface ofthe collar facing the implant receiving area, and receiving excessfixation medium with the means for receiving extravasating fixationmedium.

In further embodiments, the implant includes an elongated stem. In yetfurther embodiments, the implant includes means for capturing the collaronto the stem.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in, and constitute apart of, the specification, illustrate embodiments of the invention and,together with the description, serve to explain the objects, advantages,and principles of the invention.

FIG. 1 is a perspective view of a surgical implant in accordance with anexemplary embodiment of the present invention;

FIG. 2 is an exploded view of the implant of FIG. 1;

FIG. 3 is a perspective view of a stem of the implant of FIG. 1;

FIG. 4 is perspective view of a collar-engagement feature of the implantof FIG. 1;

FIG. 5 is a perspective view of a collar of the implant of FIG. 1;

FIG. 6 is cross-sectional view of the collar of FIG. 5 alongcross-sectional line 5-5 and looking in the direction of the arrows;

FIG. 7 is a cross-sectional view of an assembled surgical implant ofFIG. 1 along cross-sectional line 1-1 and looking in the direction ofthe arrows;

FIG. 8 is a perspective view of a surgical implant in accordance withanother exemplary embodiment of the present invention;

FIG. 9 is an exploded view of the implant of FIG. 8;

FIG. 10 is a perspective view of a stem of the implant of FIG. 8;

FIG. 11 is a cross-sectional view of a collar of the implant of FIG. 8along cross-sectional line 9-9 and looking in the direction of thearrows;

FIG. 12 is a cross-sectional view of an assembled surgical implant ofFIG. 8 along cross-sectional line 8-8 and looking in the direction ofthe arrows;

FIG. 13 is a bottom perspective view of the collar according to anembodiment of the present invention;

FIG. 14 is a cross-sectional view of another embodiment of the collar ofthe implant along cross-sectional line 13-13 and looking in thedirection of the arrows;

FIG. 15 is a cross-sectional view of the implant of FIG. 1 alongcross-sectional line 1-1 during insertion of the implant into an implantreceiving area pre-charged with fixation medium;

FIG. 16 is a cross-sectional view of the implant of FIG. 1 alongcross-sectional line 1-1 after insertion of the implant into an implantreceiving area pre-charged with fixation medium;

FIG. 17 is a perspective view of a further embodiment of the collar ofthe implant;

FIG. 18 is a perspective view of a further embodiment of the collar ofthe implant; and

FIG. 19 is a front plan view of several embodiments of stems of theimplant.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a surgical implant 10 for capturingextravasating fixation medium from an implant receiving area, alsoreferred to simply as a cavity, of a patient. The fixation medium, whichmay also be referred to as cement in shorthand, may be a polymethylmethacrylate cement, a calcium phosphate cement or a glass polyalkenoate(ionomer) cement, or any other cement or non-cement substance suitablefor fixation. The fixation medium is introduced to the implant 10 or tothe cavity in a viscous state that allows easier application. Thefixation medium then sets, or hardens, to achieve fixation. The fixationmedium may include in it, among other things, one or more antimicrobialagents to combat microbial growth.

The implant 10 is configured to be implanted into a cavity. The cavitymay be a reamed bone canal, an opening in bone either naturally orartificially created or enlarged, or any other suitable opening intissue in which the implant 10 may be received. For ease of reference,the cavity described below will be a bone canal, however, thisdisclosure is not limited to a bone canal and other cavities areenvisioned.

FIGS. 1-7 depict the surgical implant 10 according to an embodiment ofthe present invention. The implant 10 includes an elongated stem 12, acollar-engagement feature 14, and a collar 16. FIG. 1 depicts anembodiment of the implant 10 in an assembled configuration.

Referring to FIGS. 1-3 and 7 in particular, the stem 12 includes a shank18 configured to fit within a cavity of a patient and a head 20configured to receive one or more types of joint assembly componentsknown in the art. The shank 18 has a distal tip 22 and a proximate end24 opposite the distal tip 22. In an embodiment, the distal tip 22 isrounded, while in other embodiments, the distal tip 22 may becone-shaped, bullet-shaped, split-tipped or any other shape known in theart (see FIG. 19 for various examples of stem tips). In an embodiment, aplurality of flutes 26 are disposed on the shank 18. The plurality offlutes 26 extend from a position adjacent the distal tip 22 of the stem12 longitudinally along the length of the shank 18 to terminate adjacentthe proximate end 24 of the stem 12. In an embodiment, one or more ofthe plurality of flutes 26 terminate at different locations along thestem 12 with reference to one or more of the other flutes 26 (see FIG.1). In an embodiment, the plurality of flutes 26 comprises two flutesthat are located on opposite sides of the shank 18 (see FIG. 3). Inother embodiments, the plurality of flutes 26 comprises four fluteslocated equidistant from each other to form a generally cross-likeorientation (see FIG. 1). As will be evident to those skilled in theart, the flutes 26 promote adhesion and fixation of the fixation mediumto the stem 12, thereby improving overall fixation of the implant 10within the cavity of a patient. In other embodiments, the flutes 26 maybe replaced by a plurality of splines (not shown) configured to promoteimplant fixation within the cavity of the patient.

In an embodiment, the shank 18 may have a smooth exterior 15, while inother embodiments, the exterior 15 of the shank 18 is knurled, coarse orprovided with any other coating which improves fixation within thecavity of a patient. In an embodiment, the shank 18 is axially offsetfrom the head 20 (see stems 218 b, 218 d depicted in FIG. 19 forinstance) to facilitate placement of the implant 10 in cavities ofpatients having a bone structure indicating such stem. The necessity foran axially offset shank 18 can be determined by a surgeon prior toimplantation.

A seat 28 extends from the proximate end 24 of the stem 12. The seat 28includes a proximate end 30 and a distal end 32 opposite the proximateend 30. In an embodiment, the seat 28 includes a diameter larger thanthe diameter of the shank 18. In other embodiments, the diameter of theseat 28 is equal to the diameter of the shank 18.

A shoulder 34 extends from the proximate end 30 of the seat 28. Theshoulder 34 includes a proximate end 36, a distal end 38 opposite theproximate end 36, and an exterior surface 40 extending therebetween. Inan embodiment, the shoulder 34 expands radially from the centrallongitudinal axis of the stem 12 so as to form a generally conicalshape. In such embodiment, the shoulder 34 has a smaller diameter D1 atthe distal end 38 of the shoulder 34 and a larger diameter D2 at theproximate end 36 of the shoulder 34. In an embodiment, D2 is largeenough such that the proximate end 36 of the shoulder 34 forms a ridge42 that projects radially outwardly past the diameter of the head 20. Aswill be described in detail below, the exterior surface 40 and the ridge42 communicate with the collar 16 and the collar-engagement feature 14,respectively, to ensure fixed assembly of the implant 10.

The head 20 extends from the proximate end 36 of the shoulder 34. Thehead 20 includes a proximate end 44 having a diameter D3 and a distalend 46 having a diameter D4 opposite the proximate end 44. In anembodiment, the head 18 is generally cylindrical, however, otherconfigurations may be utilized such as, for example, elliptical, oval,square, rectangular and the like. In an embodiment, D4 is greater thanD3 so as to form a decreasing taper towards the proximate end 44 fromthe distal end 46, also known as a Morse taper. The degree of taper,that is, the degree of change of the diameter of the head from D4 to D3,can be varied. In such manner, embodiments of the implant 10 may bemodular and capable of receiving one or more types of joint components(not shown).

An anti-rotation feature 48 is provided to prevent rotational movementof a joint component (not shown) relative to the implant 10. Theanti-rotation feature 48 extends from the proximate end 44 of the head20, and is sized and shaped so as to cooperatively communicate with ajoint component (not shown). As is evident to those skilled in the art,therefore, the anti-rotation feature 48 and the head 20 facilitate theanti-rotational connection of a joint component (not shown) to theimplant 10.

Referring now to FIGS. 2 and 4, the collar-engagement feature 14includes a proximate end 50, a distal end 52 opposite the proximate end50, and an opening 54 extending therebetween. The opening 54 is definedby an inner surface 56 and a lip 58 extending radially inwardly adjacentthe proximate end 50 of the collar-engagement feature 14. In anembodiment, internal threads 60 are positioned on at least a portion ofthe inner surface 56. As will be described in detail below, the lip 58communicates with the ridge 42 of the shoulder 34 and the internalthreads 60 communicate with corresponding structure on the collar 16 topromote fixed assembly of the implant 10. In an embodiment, thecollar-engagement feature 14 is formed integral with the stem 12. In anembodiment, the collar-engagement feature 14 may be generally hexagonal,heptagonal or octagonal to provide locations for a surgeon to grip,thereby promoting easy rotational manipulation of the collar-engagementfeature 14. As will be evident to those skilled in the art, any otherconventional shape may be used so long as the collar-engagement feature14 provides a surgeon improved grip to facilitate rotation thereof.

Turning now to FIGS. 2 and 5-7, the collar 16 includes a proximate end62, a distal end 64 opposite the proximate end 62, an inner through bore66 extending therebetween, and an exterior surface 68. The through bore66 is sized and shaped to receive the shank 18 and the seat 28 of thestem 12. The collar 16 further includes a generally cone-shaped inneropening 70 having a first surface 72 adjacent the proximate end 62 ofthe collar 16. The opening 70 is sized and shaped to correspond to thesize and shape of the shoulder 34 such that the first surface 72 of thecollar 16 can be fitted over and made substantially flush with theshoulder 34.

The exterior surface 68 of the collar 16 includes external threads 74located adjacent the proximate end 62 of the collar 16. The externalthreads 74 correspond to internal threads 60 of the collar-engagementfeature 14 to allow for threaded engagement of the collar-engagementfeature 14 and the collar 16. A second surface 76 is located adjacentthe distal end 64 of the collar 16. In an embodiment, the second surface76 is configured to abut resected bone of a patient. A plurality ofrecesses 78 extend from the second surface 76 into the collar 16 asufficient distance to capture fixation medium extravasating from thecavity of a patient during implantation (see FIG. 16 depicting fixationmedium captured in recesses 78). The recesses 78 are generallycylindrical in shape and are arranged in a radial orientation around thesecond surface 76 of the collar 16. In an embodiment, one or more toolbearing recesses 80 are provided to accommodate a tool (not shown)configured to facilitate rotation or retention of the collar 16, therebyfacilitating threaded engagement of the collar-engagement feature 14 andthe collar 16. In an embodiment, the one or more tool bearing recesses80 extend further into the collar 16 than the plurality of recesses 78,while in other embodiments, the one or more tool bearing recesses 80extend an equal distance into the collar 16 as the plurality of recesses78. In further embodiments, the plurality of recesses 78 extend furtherinto the collar 16 than the one or more tool bearing recesses 80. In afurther embodiment, the one or more tool bearing recesses 80 can be opento the through bore 66 (see FIGS. 1, 2, and 5-7), while in still otherembodiments the one or more tool bearing recesses 80 are contained fullywithin the collar 16 (see FIGS. 11 and 13-15).

In an embodiment, the exterior surface 68 of the collar 16 can beadapted in various ways such as, for example, providing a material orcoating adapted to promote bone ingrowth or adhesion/ongrowth. Thematerial or coating may be a three-dimensional porous material 81 orporous coating as will be described in more detail below. The porousmaterial 81 may be disposed on a portion or all of the exterior surface68 of the collar 16. The cross-section of the collar 16 when viewed fromthe proximate end 62 of the collar 16 may be any conventional shape suchas, for instance, circular, oval, square or other various shapes thatmay provide an improved fit within a cavity of a patient. The secondsurface 76 of the collar 16 may also be provided in various shapes. Forinstance, in an embodiment, the second surface 76 is flat and forms a90-degree angle with the exterior surface 68 (see FIG. 5). In otherembodiments, the second surface 76 is angled with reference to theexterior surface 68 so as to provide a sloped, cone-shape to the secondsurface 76 and the distal end 64 of the collar 16. In an embodiment,this cone-shape facilitates implantation of the implant 10 into themedullary canal of a patient and can be sized and shaped to fit withinvarious portions of a patient's bone such as, for instance, thediaphysis of a patient's bone. The collar 16 may also be provided invarious lengths. Decision of optimal length of collar 16 may be made bythe surgeon prior to implantation of the implant 10.

The connection mechanism of an embodiment of the implant 10 according tothe present invention will now be described. In use, a surgeon willselect a stem 12 of a particular size and shape depending on variousfactors related to the patient known prior to implantation. Such stemmay, for instance, be straight or bowed, fluted or splined, and have asingle or split tip. FIG. 19 depicts various embodiments of stems thatcan be used in conjunction with the present invention, as will bedescribed in more detail below.

Once the stem 12 has been selected, a particularly sized and shapedcollar 16 is then selected that corresponds to the dimensions of thestem 12 and the mating bone surface. Selection of the collar 16determines the selection of collar-engagement feature 14. The size andpitch of the external threads 74 of the collar 16 determine the size andpitch of the corresponding internal threads 60 of the collar-engagementfeature 14. As will be evident to those skilled in the art, the collar16 and the collar-engagement feature 14 must be capable of fitting overthe shank 18 and seat 28 of the stem 12 and over the head 20,respectively.

Once the proper size stem 12, collar-engagement feature 14 and collar 16have been selected, they must be aligned according to the orientationdepicted in FIGS. 1, 2 and 7. The collar 16 is positioned over thedistal tip 22 of the shank 18 and is then translated longitudinallyalong the shank 18 until the collar 16 travels over the seat 28 and thefirst surface 72 of the cone-shaped opening 70 rests adjacent theshoulder 34 (see arrow A in FIG. 1 depicting movement of the collar 16).Collar-engagement feature 14 is positioned over the head 20 andtranslated longitudinally along head 20 until the lip 58 of thecollar-engagement feature 14 rests adjacent the ridge 42 of the shoulder34 (see arrow B in FIG. 1 depicting movement of the collar-engagementfeature 14). Once both the collar 16 and the collar-engagement feature14 are translated as described above, the internal threads 60 of thecollar-engagement feature 14 abut the external threads 74 of the collar16. Next, the collar-engagement feature 14 and the collar 16 arethreadedly engaged via rotating either the collar-engagement feature 14or the collar 16 such that the internal threads 60 and external threads74 interact with each other (one embodiment of this connection mechanismis shown by arrow C in FIG. 1 depicting rotational movement of thecollar 16). In an embodiment, the collar-engagement feature 14 isrestrained while a rotational force is applied to the collar 16.Conversely, the collar 16 may be restrained while a rotational force isapplied to the collar-engagement feature 14 or, in a still furtherembodiment, both the collar 16 and the collar-engagement feature 14 maybe rotated simultaneously in opposing directions. In each of these threeembodiments, rotational force is applied until the collar-engagementfeature 14 and the collar 16 are locked together. In an embodiment, atool (not shown) can be introduced into the tool bearing recesses 80 tofacilitate rotation or retention of the collar 16. During such threadedrotation, the ridge 42 and lip 58 function to ensure fixed connectionand proper positioning of the collar 16 and the collar-engagementfeature 14 along the length of the stem 12. Once assembled, the implant10 is can be implanted into a patient.

FIGS. 8-12 depict an alternative embodiment of the present inventionlabeled implant 110. Implant 110 is substantially similar to implant 10in general construction and use. As such, discussion of similaritiesbetween the implant 10 and the implant 110 will be omitted. Wherenecessary, similar elements will be labeled with the same referencenumber offset by 100. For clarity, where elements of the implant 110differ from the elements of the implant 10, such elements will be givenan odd reference number.

Referring now to FIGS. 8-10 and 12, the implant 110 includes anelongated stem 112 having a shank 118 and a head 120 and a collar 117adapted to be rotatably fixed on the stem 112. A connection member 119is positioned between the shank 118 and the head 120. The connectionmember 119 has a proximate end 121 and a distal end 123 opposite theproximate end 121. The connection member 119 has a diameter D5 adjacentthe proximate end 121 and a diameter D6 adjacent the distal end 123. Inan embodiment, the distal end 123 of the connection member 119 includesa flared seat 125 adjacent the shank 118. One or more connectionelements 127 are positioned on the connection member 119. The connectionelements 127 are configured to communicate with the collar 117 toachieve fixed assembly of the implant 110, as will be discussed in moredetail below. In an embodiment, connection elements 127 are flangespositioned opposite each other (see FIGS. 9, 10 and 12). In otherembodiments, other mechanisms of connection are envisioned such as, forinstance, an interference fit, a snap fit or any other conventionalconnection mechanism capable of connecting the collar 117 to the stem112.

In an embodiment, diameter D5 is larger than diameter D6, therebycreating a ledge 129 which acts as a stop for the collar 117. In thismanner, the collar 117 can be fitted over the shank 118 and translatedalong the length of the stem 112 until the collar 117 reaches the ledge129. In other embodiments, diameters D5 and D6 are equal and the collar117 includes additional structure (not shown) that functions as a stopto ensure the collar 117 is positioned at the proper location along thestem 112.

Turning to FIGS. 8-9 and 11-12, the collar 117 has a proximate end 131,a distal end 133 opposite the proximate end 131, an inner through bore135 extending therebetween and an exterior surface 137. The through bore135 is sized and shaped to fit over the shank 118 and the one or moreconnection elements 127. The through bore 135 includes at least oneconnection receiving element 139 adjacent the proximate end 131 of thecollar 117. The at least one connection receiving element 139 mustcorrespond to the one or more connection elements 127. Thus, in anembodiment wherein connection elements 127 are flanges, the at least oneconnection receiving element 139 is one or more corresponding threadssized and shaped to receive the flanges and lock them in place. In anembodiment, the through bore 135 includes an inner flared region 141that corresponds to the flared seat 125 of the connection member 119.

A surface 143 is located adjacent the distal end 133 of the collar 117.In an embodiment, the surface 143 is configured to abut resected bone ofa patient. A plurality of recesses 178 extend from the surface 143 intothe collar 117 a sufficient distance to capture fixation mediumextravasating from a cavity of a patient during implantation. Therecesses 178 are generally cylindrical in shape and are arranged in aradial orientation on the surface 143 of the collar 117. One or moretool bearing recesses 180 are provided to accommodate a tool (not shown)configured to facilitate rotation and/or retention of the collar 117,thereby allowing assembly of the implant 110.

The connection mechanism of an embodiment of the implant 110 accordingto the present invention, which can also be referred to as a “bayonet”style connection, will now be described. Once a surgeon has selected theparticular stem 112 as described above in reference to stem 12, anappropriately sized collar 117 is selected that corresponds to thedimensions of the chosen stem 112 and the bone mating surface of apatient's bone. The collar 117 will include the at least one connectionreceiving element 139 that corresponds to and is adapted to interactwith the one or more connection elements 127 of the chosen stem 112. Inan embodiment, the one or more connection elements 127 are flanges andthe at least one connection receiving element 139 is one or more threadscapable of receiving the flanges. In this embodiment, the collar 117 isfitted over the shank 118 and translated along the length of the stem112 until the collar 117 reaches the ledge 129 of the connection member119 (see arrow D in FIG. 8 depicting movement of the collar 117). Oncethe collar 117 reaches the ledge 129, the collar 117 may be threadedlyengaged with the stem 112 by applying a rotational force to the collar117 while the stem 112 is restrained so that the flanges of the one ormore connection elements 127 travel down the one or more threads of theat least one connection receiving element 139 (see arrow E in FIG. 8depicting movement of the collar 117). Conversely, collar 117 may berestrained while a rotational force is applied to the stem 112 or, insome embodiments, both the collar 117 and the stem 112 may be rotatedsimultaneously in opposing directions. In an embodiment, a tool (notshown) can be introduced into the tool bearing recesses 180 tofacilitate rotation and/or retention of the collar 117.

In an embodiment, the collar 117 or the stem 112 is turnedthree-quarters of a full rotation to lock the stem 112 and the collar117. In another embodiment, the collar 117 and the stem 112 each rotateto a combined magnitude of three-quarters of a full rotation to lock thestem 112 and the collar 117. In other embodiments, more or less rotationis necessary to lock the stem 112 and the collar 117. The flared seat125 and the inner flared region 141 ensure that there is space betweenthe collar 117 and the stem 112 to allow for rotation. Once fullyrotated, the implant 110 is in an assembled state and is can beimplanted into a patient.

The mechanism of fixation medium capture will now be described withreference to FIGS. 13-16. FIGS. 13-16 depict the implant 10, however,the following mechanism is similarly applicable to implant 110. Asdescribed above, the plurality of recesses 78 are disposed throughoutthe second surface 76. In an embodiment, additional vertical recesses 82may be provided so as to receive more fixation medium if necessary. Thevertical recesses 82 are sized and shaped to accommodate extravasatingfixation medium. In a further embodiment, horizontal recesses 84, whichare sized and shaped to accommodate extravasating fixation medium, areconnected to vertical recesses 82 so as to receive additional fixationmedium if necessary. As will be evident to one of ordinary skill in theart, each of the horizontal recesses 84 must be connected to at leastone of the vertical recesses 82 to provide a pathway for extravasatingfixation medium. In an embodiment, the recesses 78 are spacedequidistantly in a radial orientation throughout the collar 16. In otherembodiments, the recesses 78 may be arranged randomly throughout thecollar 16.

In practice, the cavity may be pre-machined in order to prepare thecavity for implantation of the implant 10. Fixation medium is then addedto the cavity. Alternatively, fixation medium made be added directly tothe implant 10, 110 and allowed to set until it is exhibits a malleableputty-like consistency. The implant 10, 110 is then implanted into thepatient by aligning the shank 18 with the cavity and inserting theimplant 10, 110 into the cavity. During the insertion process, excessfixation medium will be forced to extravasate from the cavity.

FIG. 15 depicts the implant 10 during insertion into a cavity of a longbone L that has been pre-charged with fixation medium FM. The implant 10causes displacement of the fixation medium FM previously introduced tothe cavity (see arrow F depicting movement of the implant 10 and arrowsG depicting movement of the fixation medium FM). Once the second surface76 contacts the extravasating fixation medium, the fixation medium FM isforced into and taken in by the plurality of recesses 78. This reducesor eliminates the amount of fixation medium FM that can escape from thecavity to reach the exterior surface 68 of the collar 16.

FIG. 16 depicts the implant 10 inserted into a cavity of a long bone Lthat has been pre-charged with fixation medium FM. The implant 10 hasdisplaced the fixation medium FM and caused the fixation medium FM toextravasate from the cavity of the long bone L. The fixation medium FMhas been taken in by the plurality of recesses 78. In this manner, theexterior surface 68 of the collar 16 retains a suitable bone ingrowthregion. As will be evident to one of ordinary skill in the art, asubstantially similar process occurs during insertion of the implant110.

FIGS. 17 and 18 depict various embodiments of exterior surfaces orcoatings to be used in conjunction with the collar 16 or the collar 117.In an embodiment, the exterior surfaces 68, 137 of the collars 16, 117,respectively, can be formed of or coated with a three-dimensional porousstructure 81. The porosity may be varied to optimize bone ingrowth andbone apposition on the collars 16, 117. The porous structure may furtherinclude randomness or have areas for soft tissue ingrowth and otherareas for hard tissue ingrowth.

In an embodiment, a porous pattern 145, such as, for instance, awaffle-pattern, may be used on the exterior surfaces 68, 137 to furtherfacilitate bone ingrowth and bone apposition on the collars 16, 117. Inother embodiments, other conventional patterns may be used. In anembodiment, the exterior surfaces 68, 137 of the collars 16, 117 arecoated with various bone-growth factors, such as hydroxyapatite or othersubstances known to stimulate bone growth. In other embodiments, theexterior surfaces 68, 137 of the collars 16, 117 are coated with one ormore antimicrobial, antibacterial, antiviral, antifungal coatings orother substances known to inhibit growth of microbial life. Similarly,the foregoing bone growth stimulating substances and the antimicrobialsubstances can be formed integral with the porous structure 81 ordispersed therein. The porous structure 81 and coatings may bebioresorbable or configured to not degrade within the body.

FIG. 19 depicts various embodiments of stems, which are labeled 212a-212 d for clarity, with differing shanks that can be incorporated intothe implants 10, 110. The leftmost stem 212 a includes a straight shank218 a with a rounded distal tip 22 a. Stem 212 b includes an offset orbowed shank portion 218 b with a rounded distal tip 22 b to be used inprocedures where the cavity indicates such the shank 218 b. Stem 212 cdepicts a shank portion 218 c having splined canals 220 c instead offlutes similar to flutes 26 and a pointed distal tip 22 c instead of therounded distal tip 22. Stem 212 d incorporates a bowed shank portion 218d similar to stem 212 b, but with a slotted tip 22 d.

Various modifications may be made to the scope of the present inventionwithout departing from the spirit thereof. For instance, the collars 16,117 may be configured with one or more areas of internal space (notshown) connecting one or more of the plurality of recesses 78, 178 andadditional recesses 82, 84 to each other, thereby increasing the maximumvolume of fixation medium that can be taken in by the implants 10, 110.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the embodimentsdescribed below be considered as exemplary only, with a true scope andspirit of the invention being indicated by the appended claims.Moreover, none of the features disclosed in this specification should beconstrued as essential elements, and therefore, no disclosed featuresshould be construed as being part of the claimed invention unless thefeatures are specifically recited in the claims. In addition, it shouldbe understood that any of the features disclosed on any particularembodiment may be incorporated in whole or in part on any of the otherdisclosed embodiments.

What is claimed is:
 1. A method of using an implant to collect excessfixation medium extravasating from an implant receiving area duringintroduction of the implant, the method comprising: a. introducing theimplant into the implant receiving area, wherein the implant includes acollar having a proximate end, a distal end opposite the proximate end,an inner through bore extending therebetween, an exterior surfaceextending between the proximate and distal ends, a distal surfacelocated adjacent the distal end and configured to abut a resected bonelocated adjacent the implant receiving area, and at least one recessconfigured to receive extravasating fixation medium, and externalthreads, an elongated stem having a distal tip and a proximate endopposite the distal tip, and a collar-engagement feature having internalthreads, wherein the collar is attached to the elongated stem, and theexternal threads of the collar are rotatably engaged with the internalthreads of the collar-engagement feature, and wherein the at least onerecess extends from the distal surface into the collar and is locatedbetween the inner through bore and the exterior surface so as to beseparated from the exterior surface; and b. contacting the distalsurface to the extravasating fixation medium such that the at least onerecess receives excess extravasating fixation medium therein.
 2. Themethod of claim 1, further comprising introducing fixation medium to theimplant receiving area prior to the introducing step.
 3. The method ofclaim 1, wherein the stem includes a radially projecting shoulder. 4.The method of claim 3, wherein the collar and the collar-engagementfeature are assembled over the shoulder prior to insertion into theimplant receiving area of a patient.
 5. A method of using an implant tocollect excess fixation medium extravasating from an implant receivingarea during introduction of the implant, the method comprising: a.assembling the implant, wherein the implant includes a collar having aproximate end, a distal end opposite the proximate end, an inner throughbore extending therebetween, an exterior surface extending between theproximate and distal ends, a distal surface located adjacent the distalend and configured to abut a resected bone located adjacent the implantreceiving area, at least one recess configured to receive extravasatingfixation medium, and external threads, an elongated stem having a distaltip and a proximate end opposite the distal tip, and a collar-engagementfeature having internal threads, wherein the implant assembling stepincludes attaching the collar to the elongated stem, and rotatablyengaging the external threads of the collar with the internal threads ofthe collar-engagement feature, and wherein the at least one recessextends from the distal surface into the collar and is located betweenthe inner through bore and the exterior surface so as to be separatedfrom the exterior surface; b. introducing the implant into the implantreceiving area; and c. contacting the distal surface to theextravasating fixation medium such that at least one recess receivesexcess extravasating fixation medium therein.
 6. The method of claim 5,further comprising introducing an amount of fixation medium to theimplant receiving area prior to the introducing step.
 7. The method ofclaim 5, wherein the implant includes a radially projecting shoulderover which the collar-engagement feature and the collar can be fixed. 8.A method of using an implant to collect excess fixation mediumextravasating from an implant receiving area during introduction of theimplant, the method comprising: a. assembling the implant, wherein theimplant includes a collar having a proximate end, a distal end oppositethe proximate end, an inner through bore extending therebetween, anexterior surface extending between the proximate and distal ends, adistal surface located adjacent the distal end and configured to abut aresected bone located adjacent the implant receiving area, a means forreceiving extravasating fixation medium, and external threads, anelongated stem having a distal tip and a proximate end opposite thedistal tip, and a collar-engagement feature having internal threads,wherein the implant assembling step includes attaching the collar to theelongated stem, and rotatably engaging the external threads of thecollar with the internal threads of the collar-engagement feature, andwherein the means for receiving extravasating fixation medium extendsfrom the distal surface into the collar and is located between the innerthrough bore and the exterior surface so as to be separated from theexterior surface; b. introducing the implant into the implant receivingarea; and c. receiving excess extravasating fixation medium with themeans for receiving extravasating fixation medium.